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Jaayson Neiuwkirk

How to Tie a WD-40 Fly: A Step-by-Step Guide for Fly Fishing

The WD-40 fly is a simple yet highly effective pattern used primarily for trout fishing, especially when mayflies are hatching. Its versatility and simplicity make it a favorite among many anglers, and it can be used as both a nymph and an emerger. While it may not look like much, the WD-40’s buggy appearance and slim profile mimic small insects, such as Baetis (blue-winged olive) nymphs, making it a must-have in any fly box.

In this blog post, I’ll walk you through how to tie the WD-40 fly, detailing the materials needed and each step of the process.



Materials Needed

  • Hook: Size 16-22 scud or emerger hook (e.g., Tiemco 2488)

  • Thread: Olive or black, 8/0 or 70 denier

  • Tail: Olive or gray mallard flank or wood duck fibers

  • Body: Thread or fine dubbing in olive, black, or brown

  • Ribbing: Fine copper or gold wire (optional)

  • Wing Case: CDC feather in gray or natural


Step-by-Step Instructions

Step 1: Secure the Hook

Place your hook into the vise and secure it tightly. Attach your thread near the hook eye and wrap it backward toward the bend of the hook in smooth, even turns.

  • Tip: Be sure to leave a little room at the hook eye for finishing the fly later.

Step 2: Add the Tail

Take a small bunch of mallard flank or wood duck fibers (about 5-6 fibers) and tie them in at the bend of the hook. The tail should be about the length of the hook shank. Once tied in, trim any excess fibers and cover the remainder with thread wraps.

  • Tip: Keep the tail fibers sparse and straight, as this adds to the fly’s delicate, buggy appearance.

Step 3: Tie in the Ribbing (Optional)

If you’re using ribbing for added durability and segmentation, tie in a length of fine copper or gold wire at the bend of the hook, and leave it hanging off the back for now. You’ll wrap it later.

Step 4: Build the Body

For the body, you can either use your thread to create a slim, tapered body or apply a small amount of fine dubbing to the thread. Olive, brown, or black dubbing are great choices to match natural mayfly nymphs or emerging insects.

  • Tip: Keep the body thin and streamlined to mimic the natural shape of the nymph.

Step 5: Add the Ribbing (Optional)

If you opted for ribbing, now is the time to wrap the wire forward in open spirals along the body. This adds durability to the fly and imitates segmentation. Once you reach the front of the body, secure the wire with a few thread wraps and trim off the excess.

Step 6: Prepare and Tie in the Wing Case

Select a CDC (Cul de Canard) feather, which will serve as the wing case and legs of the fly. Strip a small section from the feather and tie it in just behind the hook eye, allowing the feather to extend backward over the top of the body. The CDC fibers should cover about two-thirds of the body length.

  • Tip: CDC is light and airy, giving the fly a natural appearance and buoyancy in the water.

Step 7: Form the Head

Now, build a small, neat head by wrapping your thread just behind the hook eye. This will also secure the CDC wing case in place. Ensure that the head is smooth and proportional to the rest of the fly.

Step 8: Whip Finish and Trim

Once the head is formed, finish the fly by performing a whip finish or adding a few half-hitches to secure the thread. Trim off any excess thread, and add a small drop of head cement to the thread wraps for extra durability.

  • Tip: Be careful not to let the cement touch the CDC, as it can affect the fibers' natural movement in the water.


Fishing the WD-40 Fly

The WD-40 fly is incredibly versatile and can be fished in various ways:

  • As a Nymph: Fish the WD-40 below the surface using a nymph rig with an indicator. It works well in slower water where insects are emerging, and trout are feeding on nymphs near the bottom.

  • As an Emerger: You can also fish the WD-40 in the surface film to mimic emerging insects, especially during a blue-winged olive (BWO) hatch.

  • Best Times to Use: This fly is particularly effective during mayfly hatches, but it can be used year-round when fish are feeding on small insects.


Why the WD-40 Fly Works

The WD-40 may not be flashy, but its simplicity is what makes it so effective. It mimics small nymphs and emergers that trout feed on, particularly Baetis (blue-winged olives). The natural movement of the CDC wing case combined with the slim, tapered body creates a convincing imitation of emerging mayflies or other small insects. Whether you’re targeting finicky fish in slow pools or prospecting in faster water, the WD-40 fly is a reliable pattern to have in your box.


Tying the WD-40 fly is simple, but its effectiveness in the water is undeniable. With just a few materials and steps, you can tie this productive fly that works well in various conditions, especially during the cooler months when mayflies are hatching. Whether you're a beginner or a seasoned angler, adding the WD-40 to your fly box is a great way to increase your chances of success on the water.


Now that you know how to tie the WD-40 fly, give it a try next time you're out on the river, and watch the trout come to life!

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